Mass Effect is a Role-Playing Game released by Bioware. During the setup (or first run), the game tries to validate the CD Key by contacting Bioware through the Internet.

I noticed that having Vista’s ECN capability enabled can cause the validation to fail. Luckily, most users don’t face the problem as ECN is disabled by default. To check whether ECN is enabled, type in a Command Prompt:

netsh interface tcp show global

So, for those of us who use Vista with ECN, try disabling ECN for the first run of the game. This can be done by opening a Command Prompt as Administrator (done by right clicking on Command Prompt and choosing to Run as Administrator) and typing the following command:

netsh interface tcp set global ecncapability=disabled

Then run the game till it displays the Game Menu.

If you wish, you can re-enabled ECN by typing:

netsh interface tcp set global ecncapability=enabled

The same process may be required while installing the expansion for the game. The problem is most likely due to one of the intermediate routers in the Bioware network not supporting ECN. Mentioning this problem as it can be one of many problems which you could face. The problem is being discussed in the Bioware Community Forum.

Problem detected by using Sysinternals TCPViewSYN SENT not being acknowledged by Bioware Server.